1
dc1947af
DEMO MANUAL DC1947A
DESCRIPTION
LT3799-1
Offline Isolated Flyback LED
Driver with PFC
Demonstration circuit 1947A is an off-line isolated flyback
LED driver featuring
LTC
®
3799-1
. The demo board provides
a single constant current output of 1A over an LED string
voltage from 30V to 50V. It is optimized to operate over a
wide AC input voltage range (90VAC to 277VAC, 47Hz to
63Hz). It provides a high power factor (>0.9) enabling a
single design to be used worldwide. It is also designed to
comply with the IEC 61000-3-2 Class C harmonics standard
and the EN55015B conducted EMI standard.
The LT3799-1 controls an isolated flyback converter in
boundary mode. Its novel current sensing scheme deliv-
ers a well-regulated output current to the secondary side
without using an opto-coupler. Open- and shorted-LED
protection ensures long term reliability.
L
, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
PERFORMANCE SUMMARY
The LT3799-1 is available in a low profile, thermally-
enhanced 16-lead MSOP package.
The LT3799-1 data sheet gives a complete description
of the device, operation and application information. The
data sheet must be read in conjunction with this quick
start guide for demo circuit 1947A.
Design files for this circuit board are available at
http://www.linear.com/demo
(T
A
= 25°C)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Input Voltage Range
Line Frequency, 47Hz to 63Hz
90
230
277
VAC
Output Current I
OUT
V
IN
= 120VAC, V
LED
= 48V
1
A
Output Voltage
30
48
50
V
Open LED Voltage
(Note 1)
54
V
Note 1: For applications with low LED string voltage, FB pin divider resistor R4 and output clamp D9 can be adjusted to reduce the open voltage limit.
See “Protection from Open LED and Shorted LED Faults” section in the data sheet for detail.
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